1. Field of Inventions
The present inventions relate generally to ambulatory infusion devices.
2. Description of the Related Art
Ambulatory infusion devices, such as implantable infusion devices and externally carried infusion devices, have been used to provide a patient with a medication or other substance (collectively “infusible substance”) in accordance with a delivery profile that specifies one or more flow rates during the delivery profile cycle, and frequently include a reservoir and a fluid transfer device. The reservoir is used to store the infusible substance and is coupled to the fluid transfer device which is, in turn, connected to an outlet port. A catheter, which has at least one outlet at the target body region, may be connected to the outlet port. As such, infusible substance in the reservoir may be transferred from the reservoir to the target body region by way of the fluid transfer device and catheter. Some fluid transfer devices, such as those which include electromagnet pumps, are configured to deliver only a single (i.e., non-adjustable) volume during each actuation, while others are configured such that the volume delivered can be adjusted from one actuation to another.
One important aspect of an ambulatory infusion device is accuracy, i.e., whether or not the infusion device is actually delivering the volume specified by the delivery profile to the outlet port. In some implantable infusion devices, delivery accuracy can only be evaluated at the time of refill when the clinician is able to compare the expected delivery volume (based on the delivery profile) with actually delivered volume. Refills typically occur only once every three months. Given that the labeled accuracy of implantable infusion devices are frequently ±15%, attempts have been made to monitor actual delivery with the infusion device itself and to automatically compensate for actual delivery volume that deviates from the volume associated with the delivery profile. Although useful, the present inventors have determined that conventional methods and apparatus for monitoring delivery and responding to delivery inaccuracy are susceptible to improvement.